Hydrocarbon conversion catalyst composition and processes therefor and therewith

ABSTRACT

A catalyst composition, a process for producing the composition, and a hydrotreating process for converting a hydrocarbon stream such as, for example, gasoline, to olefins and C 6  to C 8  aromatic hydrocarbons such as toluene and xylenes are disclosed. The catalyst composition comprises a zeolite, a clay, and optionally a coke suppressor and/or an activity promoter. The process for producing the composition comprises the steps: (1) optionally contacting a zeolite with steam whereby a steamed zeolite is formed; (2) optionally contacting a zeolite or the steamed zeolite with an acid to produce an acid-leached zeolite; (3) combining a zeolite, which can also be the steamed zeolite or the acid-leached zeolite, with a clay under a condition sufficient to bind the clay to the zeolite to produce a clay-bound zeolite; and (4) calcining the clay-bound zeolite to produce a calcined clay-bound zeolite. The hydrotreating process comprises contacting a hydrocarbon stream with the catalyst composition under a condition sufficient to effect the conversion of a hydrocarbon to an olefin and a C 6  to C 8  aromatic hydrocarbon.

FIELD OF THE INVENTION

This invention relates to a composition useful for converting ahydrocarbon to a C₆ to C₈ aromatic hydrocarbon and an olefin, to aprocess for producing the composition, and to a process for using thecomposition for converting a hydrocarbon to a C₆ to C₈ aromatichydrocarbon and an olefin.

BACKGROUND OF THE INVENTION

It is well known to those skilled in the art that aromatic hydrocarbonsand olefins are each a class of very important industrial chemicalswhich find a variety of uses in petrochemical industry. It is also wellknown to those skilled in the art that catalytically crackinggasoline-range hydrocarbons produces lower olefins such as, for example,propylene; and aromatic hydrocarbons such as, for example, benzene,toluene, and xylenes (hereinafter collectively referred to as BTX) inthe presence of catalysts which contain a zeolite. The product of thiscatalytic cracking process contains a multitude of hydrocarbonsincluding unconverted C₅ + alkanes; lower alkanes such as methane,ethane, and propane; lower alkenes such as ethylene and propylene; C₆-C₈ aromatic hydrocarbons; and C₉ + aromatic compounds which contain 9or more carbons per molecule. Recent efforts to convert gasoline to morevaluable petrochemical products have therefore focused on improving theconversion of gasoline to olefins and aromatic hydrocarbons by catalyticcracking in the presence of zeolite catalysts. For example, agallium-promoted zeolite ZSM-5 has been used in the so-called CyclarProcess to convert a hydrocarbon to BTX.

Olefins and aromatic hydrocarbons can be useful feedstocks for producingvarious organic compounds and polymers. However, the weight ratio ofolefins to aromatic compounds produced by the conversion process isgenerally less than 50%. Additionally, a zeolite catalyst is generallydeactivated in a rather short period, especially in a high sulfur and/orhigh polyaromatic environment, because of depositions of carbonaceousmaterial, generally coke, on the surface of the catalyst. Moreover, theBTX purity in the product is generally not desirably high. Therefore,development of a catalyst and a process for converting hydrocarbons tothe more valuable olefins and BTX and for reducing coke deposition wouldbe a significant contribution to the art and to the economy.

SUMMARY OF THE INVENTION

An object of this invention is to provide a catalyst composition whichcan be used to convert a hydrocarbon to a C₆ to C₈ aromatic hydrocarbonand an olefin. Also an object of this invention is to provide a processfor producing the catalyst composition. Another object of this inventionis to provide a process which can employ the catalyst composition toconvert a hydrocarbon to an olefin and a C₆ to C₈ aromatic hydrocarbon.An advantage of the catalyst composition is that it enhances the ratioof produced olefins to BTX. Another advantage of the catalystcomposition is that it suppresses the deposition of coke during ahydrotreating process. Other objects and advantages will becomes moreapparent as this invention is more fully disclosed hereinbelow.

According to a first embodiment of the present invention, a compositionwhich can be used as a catalyst for converting a hydrocarbon or ahydrocarbon mixture to an olefin and a C₆ to C₈ aromatic hydrocarbon isprovided. The composition comprises a zeolite, a clay, and optionally acoke suppressor selected from the group consisting of tin oxides,diatomaceous earth, and combination of two or more thereof.

According to a second embodiment of the present invention, a processwhich can be used for producing a catalyst composition is provided. Theprocess comprises the steps: (1) optionally contacting a zeolite withsteam whereby a steamed zeolite is formed; (2) optionally contacting azeolite or the steamed zeolite with an acid in an amount and under acondition effective to produce an acid-leached zeolite; (3) combining azeolite, which can also be the steamed zeolite or the acid-leachedzeolite, with a clay under a condition sufficient to bind the clay tothe zeolite to produce a clay-bound zeolite; and (4) calcining theclay-bound zeolite to produce a calcined clay-bound zeolite. Optionallythe clay can further comprise a coke suppressor selected from the groupconsisting of a tin oxide, diatomaceous earth, and combinations of twoor more thereof.

According to a third embodiment of the present invention, a processwhich can be used for converting a hydrocarbon or a hydrocarbon mixtureto an olefin and a C₆ to C₈ aromatic hydrocarbon is provided whichcomprises, consists essentially of, or consists of, contacting a fluidwhich comprises a hydrocarbon or a hydrocarbon mixture with a catalystcomposition, which can be the same as disclosed above in the firstembodiment of the invention, under a condition effective to convert ahydrocarbon to an olefin and an aromatic hydrocarbon containing 6 to 8carbon atoms per molecule wherein the weight ratio of the olefin toaromatic compound is enhanced.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst composition of the first embodiment of the presentinvention can comprise, consist essentially of, or consist of a zeoliteand a clay. According to the present invention the weight ratio of clayto zeolite can be any ratio that can enhance the production of an olefinfrom a hydrocarbon and can be in the range of from about 1:20 to about20:1, preferably about 1:10 to about 10:1, and most preferably about 1:5to about 5:1. The composition can also comprise, consist essentially of,or consist of, a zeolite, a clay, and a coke suppressor selected fromthe group consisting of a tin oxide, diatomaceous earth, andcombinations of two or more thereof. The weight ratio of coke suppressorto zeolite, if present, can be the same as the ratio of clay to zeolitedisclosed above. The composition can also comprise, consist essentiallyof, or consist of a zeolite, a clay, a suppressor, and a binder. Theweight of the binder generally can be in the range of from about 1 toabout 50, preferably about 5 to about 40, and most preferably 5 to 35grams per 100 grams of the composition.

Any binders known to one skilled in the art for use with a zeolite aresuitable for use herein. Examples of suitable binders include, but arenot limited to, aluminas such as for example α-alumina and γ-alumina;silicas; alumina-silica; aluminum phosphate; aluminum chlorohydrate; andcombinations of two or more thereof. Because these binders are wellknown to one skilled in the art, description of which is omitted herein.The presently preferred binder, if employed, is alumina because it isreadily available.

The composition can further be characterized by having the followingphysical characteristics: a surface area as determined by the BET methodusing nitrogen in the range of from about 300 to about 600, preferably350 to 500 m² /g; a pore volume in the range of from about 0.4 to about0.8, preferably about 0.5 to about 0.75, and most preferably 0.6 to 0.75ml/g; an average pore diameter in the range of from about 70 to about300, preferably about 100 to about 250, and most preferably 125 to 200Å; and a porosity of more than about 50%.

Any clay that can enhance the production of olefins in the conversion ofa hydrocarbon to an aromatic compound can be used. Examples of claysinclude, but are not limited to, kaolinite, halloysite, vermiculite,chlorite, attapulgite, smectite, montmorillonite, illite, saconite,sepiolite, palygorskite, and combinations of any two or more thereof.The presently preferred clay is montmorillonite which is commonlypresent in bentonite.

Any commercially available zeolite which can catalyze the conversion ofa hydrocarbon to an aromatic compound and an olefin can be employed inthe present invention. Examples of suitable zeolites include, but arenot limited to, those disclosed in Kirk-Othmer Encyclopedia of ChemicalTechnology, third edition, volume 15 (John Wiley & Sons, New York, 1991)and in W. M. Meier and D. H. Olson, "Atlas of Zeolite Structure Types,"pages 138-139 (Butterworth-Heineman, Boston, Mass., 3rd ed. 1992).Optionally a zeolite can be steam- and/or acid-treated before using thepresent invention. The presently preferred zeolites are those havingmedium pore sizes and having the physical characteristics disclosedabove. ZSM-5 and similar zeolites that have been identified as having aframework topology identified as MFI are particularly preferred becauseof their shape selectivity.

The composition can also comprise, consist essentially of, or consist ofa zeolite, a clay, a coke suppressor, and an activity promoter. Thescope and definition of zeolite, clay, or coke suppressor are the sameas those disclosed above. Any promoter that can enhance the productionof olefins in an aromatization process which converts a hydrocarbon or amixture of hydrocarbons into aromatic hydrocarbons can be used. Examplesof such promoters include, but are not limited to, sulfur, phosphorus,silicon, boron, tin, zinc, titanium, zirconium, molybdenum, lanthanum,cesium, an oxide thereof, and combinations of two or more thereof. Thepromoter can be present in the composition in the range of from about0.01 to about 10 grams per 100 grams of the composition.

The composition of the present invention can be prepared by combining azeolite, a clay, optionally a coke suppressor and/or a binder and/or anactivity promoter in the weight ratios or percent disclosed above underany conditions sufficient to effect the production of such acomposition.

However, it is presently preferred that the composition of the presentinvention be produced by the process disclosed in the second embodimentof the invention. A zeolite can be optionally combined with a binderdisclosed above under a condition sufficient to produce a zeolite-bindermixture.

According to the present invention, a zeolite, preferably a ZSM-5zeolite, a clay, and optionally a coke suppressor, and/or an activitypromoter, and/or binder can be well mixed by any means known to oneskilled in the art such as stirring, blending, kneading, or extrusion,generally in a liquid such as water, following which the resultingmixture can be dried in air at a temperature in the range of from about20° to about 800° C., for about 0.5 to about 50 hours under anypressures that accommodate the temperatures, preferably underatmospheric pressure. Thereafter, the dried, zeolite-binder mixture canbe further calcined, if desired, in air at a temperature in the range offrom about 300° to 1000° C., preferably about 350° to about 750° C., andmost preferably 450° to 650° C. for about 1 to about 30 hours to preparethe present composition.

Generally a zeolite, before a binder is combined with the zeolite, canalso be calcined under similar conditions to remove any contaminants, ifpresent, to prepare a calcined zeolite.

A zeolite, whether it has been calcined or contains a binder, can alsobe treated with steam. The treatment of a zeolite, which can contain abinder, with steam can be carried out in any suitable container orvessel known to one skilled in the art at about 100° C. to about 1000°C. under any pressure that can accommodate the temperatures to produce asteamed zeolite.

A zeolite, whether it has been steamed or not, can be treated with anacid before the preparation of the present composition. Generally, anyorganic acids, inorganic acids, or combinations of any two or morethereof can be used in the process of the present invention so long asthe acid can reduce the aluminum content in the zeolite. The acid canalso be a diluted aqueous acid solution. Examples of suitable acidsinclude, but are not limited to sulfuric acid, hydrochloric acid, nitricacid, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid,trichloroacetic acid, p-toluenesulfonic acid, methanesulfonic acid,partially or fully neutralized acids wherein one or more protons havebeen replaced with, for example, a metal (preferably an alkali metal) orammonium ion, and combinations of any two or more thereof. Examples ofpartially or fully neutralized acids include, but are not limited to,sodium bisulfate, sodium dihydrogen phosphate, potassium hydrogentartarate, ammonium sulfate, ammonium chloride, ammonium nitrate, andcombinations thereof. The presently preferred acids are hydrochloricacid and nitric acid for they are readily available.

Any methods known to one skilled in the art for treating a solidcatalyst with an acid can be used in the acid treatment of the presentinvention. Generally, a zeolite material, whether or not it contains abinder, or has been steamed, can be suspended in an acid solution. Theconcentration of the zeolite in the acid solution can be in the range offrom about 0.01 to about 500, preferably about 0.1 to about 400, morepreferably about 1 to about 350, and most preferably 5 to 300 grams perliter. The amount of acid required is the amount that can maintain thesolution in acidic pH during the treatment. Preferably the initial pH ofthe acid solution containing a zeolite is adjusted to lower than about6, preferably lower than about 5, more preferably lower than about 4,and most preferably lower than 3. Upon the pH adjustment of thesolution, the solution can be subjected to a treatment at a temperaturein the range of from about 30° C. to about 200° C., preferably about 50°C. to about 150° C., and most preferably 70° C. to 120° C. for about 10minutes to about 30 hours, preferably about 20 minutes to about 25hours, and most preferably 30 minutes to 20 hours. The treatment can becarried out under a pressure in the range of from about 1 to about 10atmospheres (atm), preferably about 1 atm so long as the desiredtemperature can be maintained. Thereafter, the acid-treated zeolitematerial can be washed with running water for 1 to about 60 minutesfollowed by drying, at about 50 to about 1000, preferably about 75 toabout 750, and most preferably 100° to 650° C. for about 0.5 to about15, preferably about 1 to about 12, and most preferably 1 to 10 hours,to produce an acid-leached zeolite. Any drying method known to oneskilled in the art such as, for example, air drying, heat drying, spraydrying, fluidized bed drying, or combinations of two or more thereof canbe used.

The dried, acid-leached zeolite can also be further washed, if desired,with a mild acid solution such as, for example, ammonium nitrate whichis capable of maintaining the pH of the wash solution in acidic range.The volume of the acid generally can be the same volume as thatdisclosed above. The mild acid treatment can also be carried out undersubstantially the same conditions disclosed in the acid treatmentdisclosed above. Thereafter, the resulting solid can be washed and driedas disclosed above.

It should be noted that, a zeolite can be acid-leached before it istreated with steam.

The dried, acid-leached zeolite, whether it has been further washed witha mild acid or not, can be calcined, if desired, under a condition knownto those skilled in the art. Generally such a condition can include atemperature in the range of from about 250 to about 1,000, preferablyabout 350 to about 750, and most preferably 450° to 650° C. and apressure in the range of from about 0.5 to about 50, preferably about0.5 to about 30, and most preferably 0.5 to 10 atmospheres (atm) forabout 1 to about 30 hours, preferably about 2 to about 20 hours, andmost preferably 3 to 15 hours.

A zeolite, a calcined zeolite, or a calcined zeolite-binder mixture, oran acid-leached zeolite, can be treated with a compound containing anexchangeable ammonium ion to prepare an ammonium-exchanged zeolite.Whether a zeolite is calcined or contains a binder, the process ortreatment in the second embodiment is the same for each. For theinterest of brevity, only a zeolite is described hereinbelow. Examplesof suitable ammonium-containing compounds include, but are not limitedto, ammonium sulfate, ammonium chloride, ammonium nitrate, ammoniumbromide, ammonium fluoride, and combinations of any two or more thereof.Treatment of the zeolite replaces the original ions such as, forexample, alkali or alkaline earth metal ions of the zeolite, withpredominantly ammonium ions. Techniques for such treatment are wellknown to one skilled in the art such as, for example, ion exchange ofthe original ions. For example, a zeolite can be contacted with asolution containing a salt of the desired replacing ion or ions.

Generally, a zeolite can be suspended in an aqueous solution of anammonium-containing compound. The concentration of the zeolite in theaqueous solution can be in the range of from about 0.01 to about 800,preferably about 0.1 to about 500, more preferably about 1 to about 400,and most preferably 5 to 100 grams per liter. The amount of theammonium-containing compound required depends on the amount of theoriginal ion(s) to be exchanged. Upon the preparation of the solution,the solution can be subject to a temperature in the range of from about30° C. to about 200° C., preferably about 40° C. to about 150° C., andmost preferably 50° C. to 125° C. for about 1 to about 100 hours,preferably about 1 to about 50 hours, and most preferably 2 to 25 hoursdepending on desired degrees of ion exchange. The treatment can becarried out under a pressure in the range of from about 1 to about 10atmospheres (atm), preferably about 1 atm or any pressure that canmaintain the required temperature. Thereafter, the treated zeolite canbe washed with running water for 1 to about 60 minutes followed bydrying and calcining to produce calcined hydrogen-form zeolite. For thepreparation of a calcined zeolite or zeolite-binder the drying andcalcining processes can be carried out substantially the same as thosedisclosed above.

Generally, the ammonium-exchanged zeolite becomes hydrogen exchangedupon calcination or high temperature treatment such that a predominantproportion of its exchangeable cations are hydrogen ions. Theabove-described ion exchange of exchangeable ions in a zeolite is wellknown to one skilled in the art, therefore, the description of which isomitted herein for the interest of brevity.

In the second embodiment of the invention, a zeolite or a zeolite-bindermixture, which could have been steamed and/or acid-leached, in a desiredionic form, regardless whether calcined or not, can be combined with aclay and optionally a coke suppressor by the process disclosed above forproducing zeolite-binder mixture to produce the composition of theinvention. The composition can then be contacted with an activitypromoter precursor compound, preferably in a solution or suspension,under a condition known to those skilled in the art to incorporate apromoter precursor compound into a zeolite. Preferably the promoterprecursor compound is impregnated onto the zeolite or the composition ofthe invention. Because the methods for incorporating or impregnating apromoter precursor compound into a zeolite a solid composition such as,for example, impregnation by incipient wetness method, are well known tothose skilled in the art, the description of which is also omittedherein for the interest of brevity.

According to the present invention, any activity promoter precursorcompound, which upon being incorporated into, or impregnated or coatedonto, a zeolite or zeolite-binder mixture can be converted into anactivity promoter, as disclosed in the first embodiment of thisinvention, upon calcining, can be used in the present invention.Presently it is preferred that a promoter precursor be selected from thegroup consisting of sulfur-containing compounds, phosphorus-containingcompounds, boron-containing compounds, magnesium-containing compounds,tin-containing compounds, titanium-containing compounds,zirconium-containing compounds, molybdenum-containing compounds,germanium-containing compounds, indium-containing compounds,lanthanum-containing compounds, cesium-containing compounds, andcombinations of two or more thereof. Because these precursor compoundsand the incorporation thereof into a zeolite are well known to oneskilled in the art, disclosure of which is omitted herein for theinterest of brevity.

Upon the incorporation or impregnation of the promoter precursorcompound onto the zeolite or zeolite-binder mixture to produce apromoter precursor-incorporated or -impregnated zeolite, the promoterprecursor-incorporated or -impregnated zeolite can be subject tocalcination under a condition that can include a temperature in therange of from about 300° C. to about 1000° C., preferably about 350° C.to about 750° C., and most preferably 400° C. to 650° C. under apressure that accommodates the temperature, generally in the range offrom about 1 to about 10 atmospheres (atm), preferably about 1 atm for aperiod in the range of from about 1 to about 30, preferably about 1 toabout 20, and most preferably 1 to 15 hours to produce the compositionof the invention.

The composition of the invention then can be, if desired, pretreatedwith a reducing agent before being used in a process for converting ahydrocarbon to an olefin and an aromatic hydrocarbon. The presentlypreferred reducing agent is a hydrogen-containing fluid which comprisesmolecular hydrogen (H₂) in the range of from 1 to about 100, preferablyabout 5 to about 100, and most preferably 10 to 100 volume %. Thereduction can be carried out at a temperature, in the range of fromabout 250° C. to about 800° C. for about 0.1 to about 10 hourspreferably about 300° C. to about 700° C. for about 0.5 to about 7hours, and most preferably 350° C. to 650° C. for 1 to 5 hours.

According to the third embodiment of the present invention, a processuseful for converting a hydrocarbon or a hydrocarbon mixture to amixture rich in olefins and C₆ to C₈ aromatic hydrocarbons comprises,consists essentially of, or consists of contacting a fluid streamcomprising a hydrocarbon or hydrocarbon mixture which can compriseparaffins, olefins, naphthenes, and aromatic compounds with a catalystcomposition under a condition sufficient to effect the conversion of ahydrocarbon mixture to a mixture rich in olefins and C₆ to C₈ aromatichydrocarbons or to enhance the weight ratio of olefins (ethylene andpropylene) to the C₆ to C₈ aromatic compounds. The fluid stream alsocomprises a diluent selected from the group consisting of carbondioxide, nitrogen, helium, carbon monoxide, steam, hydrogen, andcombinations of two or more thereof. The presently preferred diluentsare nitrogen and carbon dioxide for they are readily available andeffective. The catalyst composition can be the same as that disclosed inthe first embodiment of the invention and can be produced by the secondembodiment of the invention. The weight ratio of the diluent to thehydrocarbon is in the range of from about 0.01:1 to about 10:1,preferably about 0.051 to about 5:1, and most preferably 0.1:1 to about2:1.

The term "fluid" is used herein to denote gas, liquid, vapor, orcombinations thereof. The term "hydrocarbon" is generally referred to,unless otherwise indicated, as one or more hydrocarbons having fromabout 4 carbon atoms to about 30 carbon atoms, preferably about 5 toabout 20 carbon atoms, and most preferably 5 to 16 carbon atoms permolecule. The term "enhance or enhanced" refers to an increased weightratio of olefins to BTX employing the catalyst composition as comparedto employing a zeolite such as commercially available ZSM-5 andgenerally the increased weight ratio is greater than 1:1, preferably2:1. Examples of a hydrocarbon include, but are not limited to butane,isobutane, pentane, isopentane, hexane, isohexane, cyclohexane, heptane,isoheptane, octane, isooctane, nonane, decane, undecane, dodecane,tridecane, tetradecane, pentadecane, hexadecane, butenes, isobutene,pentenes, hexenes, benzene, toluene, ethylbenzene, xylenes, andcombinations of any two or more thereof.

Any fluid which contains a hydrocarbon as disclosed above can be used asthe feed for the process of this invention. Generally, the fluid feedstream can also contain olefins, naphthenes (cycloalkanes), or somearomatic compounds. Examples of suitable, available fluid feeds include,but are not limited to, gasolines from catalytic oil cracking processes,pyrolysis gasolines from thermal cracking of saturated hydrocarbons,naphthas, gas oils, reformates, and combinations of any two or morethereof. The origin of this fluid feed is not critical. Thoughparticular composition of a feed is not critical, a preferred fluid feedis derived from gasolines which generally contain more paraffins(alkanes) than combined content of olefins and aromatic compounds (ifpresent).

The contacting of a fluid feed stream containing a hydrocarbon with thecatalyst composition can be carried out in any technically suitablemanner, in a batch or semicontinuous or continuous process, under acondition effective to convert a hydrocarbon to a C₆ to C₈ aromatichydrocarbon. Generally, a fluid stream as disclosed above, preferablybeing in the vaporized state, is introduced into an aromatizationreactor having a fixed catalyst bed, or a moving catalyst bed, or afluidized catalyst bed, or combinations of any two or more thereof byany means known to one skilled in the art such as, for example,pressure, meter pump, and other similar means. Because an aromatizationreactor and aromatization are well known to one skilled in the art, thedescription of which is omitted herein for the interest of brevity. Thecondition can include an hourly space velocity of the fluid stream inthe range of about 0.01 to about 100, preferably about 0.05 to about 50,and most preferably 0.1 to 30 g feed/g catalyst/hour. Generally, thepressure can be in the range of from about 0 to about 1000 psig,preferably about 0 to about 200 psig, and most preferably 0 to 50 psig,and the temperature is about 250° to about 1000° C., preferably about350° to about 750° C., and most preferably 450° to 650° C.

The process effluent generally contains a light gas fraction comprisinghydrogen and methane; a C₂ -C₃ fraction containing ethylene, propylene,ethane, and propane; an intermediate fraction including non-aromaticcompounds higher than 3 carbon atoms; and a BTX aromatic hydrocarbonsfraction (benzene, toluene, ortho-xylene, meta-xylene and para-xylene).Generally, the effluent can be separated into these principal fractionsby any known methods such as, for example, fractionation distillation.Because the separation methods are well known to one skilled in the art,the description of which is omitted herein. The intermediate fractioncan be recycled to an aromatization reactor described above, methane,ethane, and propane can be used as fuel gas or as a feed for otherreactions such as, for example, in a thermal cracking process to produceethylene and propylene. The olefins can be recovered and furtherseparated into individual olefins by any method known to one skilled inthe art. The individual olefins can then be recovered and marketed. TheBTX fraction can be further separated into individual C₆ to C₈ aromatichydrocarbon fractions. Alternatively, the BTX fraction can undergo oneor more reactions either before or after separation to individual C₆ toC₈ hydrocarbons so as to increase the content of the most desired BTXaromatic hydrocarbon. Suitable examples of such subsequent C₆ to C₈aromatic hydrocarbon conversions are disproportionation of toluene (toform benzene and xylenes), transalkylation of benzene and xylenes (toform toluene), and isomerization of meta-xylene and/or ortho-xylene topara-xylene.

After the catalyst composition has been deactivated by, for example,coke deposition or feed poisons, to an extent that the feed conversionand/or the selectivity to the desired ratios of olefins to BTX havebecome unsatisfactory, the catalyst composition can be reactivated byany means known to one skilled in the art such as, for example,calcining in air to bum off deposited coke and other carbonaceousmaterials, such as oligomers or polymers, preferably at a temperature ofabout 400° to about 650° C. The optimal time periods of the calciningdepend generally on the types and amounts of deactivating deposits onthe catalyst composition and on the calcination temperatures. Theseoptimal time periods can easily be determined by those possessingordinary skills in the art and are omitted herein for the interest ofbrevity.

The following examples are presented to further illustrate thisinvention and are not to be construed as unduly limiting the scope ofthe present invention.

EXAMPLE I

This example illustrates the preparation of catalyst composition of theinvention.

A ZSM-5 zeolite obtained from UCI (United Catalysts, Inc., Louisville,Ky.) having a product designation of T-4480 (obtained as a 1/16 inchextrudate) was used as control catalyst (catalyst A). Zeolite T-4480contained 30 percent by weight of alumina as binder.

A ZSM-5 zeolite obtained from CU Chemie Uetikon AG, Uetikon, Switzerlandhaving a product designation of Zeocat PZ 2/50H (obtained as powder) wasused to produce other catalyst compositions.

First, the zeolite powder was extruded, following the addition of justenough water to make a paste, to produce 1/16 inch extrudates which werecalcined at 500° C. for 3 hours (catalyst B).

Secondly, 5 g of the Zeocat zeolite powder was mixed with 5 g ofbentonite. Following the addition of just enough water to make a paste,the paste was extruded. The extrudates were heated to and at 500° C. for3 hours in a muffle furnace to produce 10 g of a zeolite containing clay(catalyst C).

In another preparation, powder PZ 2/50H zeolite (24 g) was mixed with 6g of bentonite to form a mixture followed by the addition of just enoughwater to form a paste. The paste was then extruded, dried, and calcinedat 500° C. for 3 hours to produce 30 g of a zeolite containing 20 weight% clay (catalyst D).

Still in another preparation, 10 g of PZ 2/50H was mixed with 2 g ofbentonite followed by the procedure described above for Catalyst C toproduce 12 g of a zeolite containing 16.7 weight % clay (catalyst E).

In a separate run, 20 g of PZ 2/50H powder zeolite was thoroughly mixedwith 5 g of bentonite. Following the procedure described above forproducing catalyst C, a zeolite (total 25 g) was produced (catalyst F)which contained 20 weight % clay by calculation.

Also in a separate run, 20 g of Zeocat zeolite PZ 2/50H was mixed with 5g of stannous oxide and 5 g of bentonite to form a mixture. Followingthe procedure described above for Catalyst C, a zeolite (catalyst G) (30g) containing 16.7 weight % tin and 16.7 weight % clay was produced.

Still in a separate run, 20 g of PZ 2/50H powder, 5 g of diatomaceousearth, and 5 g of bentonite were thoroughly mixed. Following theprocedure described above for the production of catalyst C, a zeolite(catalyst H) containing 16.7 weight % diatomaces earth and 16.7 weight %clay was produced.

EXAMPLE II

This example illustrates the use of the catalyst compositions describedin Example I as catalysts in the conversion of hydrocarbons to olefinsand BTX.

A quartz reactor tube (inner diameter 1 centimeter; length 60centimeter) was filled with a 20 centimeter bottom layer of Alundum®alumina (inert, low surface area alumina), 4.4 grams of one of thecatalysts in the middle 20 centimeter of the tube, and a 20 centimetertop layer of Alundum® alumina. The liquid feed was a gasoline obtainedfrom Phillips Petroleum Company, Bartlesville, Okla., and containedhydrocarbons shown in Table I. The liquid feed shown in Table I issummarized as: 38.7 weight percent (%) lights (C₅ s and C₆ s); 1.3%benzene; 5.4% toluene; 8.1% C₈ aromatics; 38.9% nonaromatics in BTXboiling range; and 25.9% heavies (C₈ +). The feed was introduced intothe reactor at a rate of 12 ml/hour (8.95 g/hour). The reactiontemperature was 600° C. The reactor effluent was cooled and separatedinto a gaseous phase and a liquid phase by passing through a wet icetrap for liquid product collection and then through a wet test meter forgas volume measurement. The liquid was weighed hourly and analyzed on aHewlett-Packard 5890 gas chromatograph equipped with a fused silicacolumn (DB-1). The gas was sampled hourly after the ice trap andanalyzed on a Hewlett-Packard 5890 gas chromatograph using a HP-PLOT/Al₂O₃ column. The gas was also analyzed for hydrogen content on a Carle gaschromatograph using hydrocarbon trap followed by a 13 X molecular sievecolumn. Both phases were analyzed by gas chromatographs at intervals ofabout 1 hour. About 2 hours after the feed was started, reactor effluentwas again sampled and analyzed by gas chromatography for olefins and BTXcontent. The results of the runs at about 6 hours were shown in Table IIbelow which illustrates the production of olefins and BTX from the TableI feed and individual catalyst compositions produced in Example I.

                  TABLE I    ______________________________________    Hydrocarbon Analysis of Catalytically Cracked Gasoline    ______________________________________         n-paraf-                 Iso-            Naph-         fins    paraffins                          Aromatics                                 thenes                                       Olefins Total    C.sub.1         0.000   0.000    0.000  0.000 0.000   0.000    C.sub.2         0.000   0.000    0.000  0.000 0.000   0.000    C.sub.3         0.000   0.000    0.000  0.000 0.000   0.000    C.sub.4         0.000   0.000    0.000  0.000 0.018   0.018    C.sub.5         1.292   8.147    0.000  0.169 10.741  20.348    C.sub.6         0.749   7.164    1.266  1.972 7.135   18.287    C.sub.7         0.740   4.576    5.354  2.746 6.483   19.899    C.sub.8         0.760   3.234    8.120  2.531 0.830   15.475    C.sub.9         0.187   2.070    8.187  0.708 0.125   11.278    C.sub.10         0.163   1.193    5.155  0.072 0.048   6.631    C.sub.11         0.153   0.307    3.606  0.191 0.000   4.257    C.sub.12         0.115   0.974    0.768  0.088 0.000   1.946    C.sub.13         0.048   0.000    0.000  0.000 0.000   0.048    C.sub.14         0.000   0.000    0.000  0.000 0.000   0.000    Total         4.208   27.664   32.457 8.478 23.381  98.188                                       Total C.sub.15 +                                               0.108                                       Total   1.704                                       Unknowns:    ______________________________________

                  TABLE II    ______________________________________    Olefins and BTX Production (weight percent in product)               Product yield (wt %)                                               Olefin    Catalyst     C.sub.2.sup.=                        C.sub.3.sup.=                               BTX  Total                                         % Coke                                               BTX    ______________________________________    A (T4480)    6.4    6.8    42   54.7 4.4   .31    B (PZ 2/50H) 6.6    8.5    38   53.1 4.9   .40    C (PZ 2/50H + clay)                 7.0    12.0   26   46.0 ND    .77    D (PZ 2/50H + clay)                 9.8    8.9    41   59.7 1.7   .46    E (PZ 2/50H + clay)                 6.6    5.4    44   56.0 1.2   .39    F (PZ 2/50H + clay)                 7.8    6.8    42   56.6 1.2   .35    G (PZ 2/50H + clay +                 4.4    11.8   35   51.2 0.4   .46    SnO)    H (PZ 2/50H + clay +                 9.2    12.9   30   52.1 0.8   .74    diatomaceous    ______________________________________     The WHSV (weight hourly space velocity) of gasoline feed for each run was     2; coke was determined at the end of the reaction by removing the     catalysts from the reactor and determined with a thermal gravimetric     analyzer (TGA), manufactured by TA Instruments, New Castle, Delaware; ND,     not determined

Table II shows that commercial ZSM-5 zeolite (catalyst A) containingalumna binder had a high coke yield in a gasoline aromatizationreaction. Table II also shows that a ZSM-5 zeolite (catalyst B) whichdid not contain alumina binder also had a high coke yield. Addition of abentonite clay at various concentrations (catalysts D to F)significantly lowered the amount of coke yield. Table II further showsthat decreasing the ratio of zeolite to clay increased the ratio ofolefins to BTX in the product stream (catalysts C and D). The resultspresented in Table II further demonstrate that a zeolite containing clayand either stannous oxide (catalyst G) or diatomaceous earth (catalystH) not only significantly further reduced the coke formation but alsoincreased the ratio of olefins to BTX.

EXAMPLE III

This example illustrates another embodiment of the invention.

A Zeocat zeolite (catalyst I) containing about 70 weight % PZ 2/50Hzeolite and 30% clay binder was a commercially available productobtained as 1/16 inch extrudates.

Catalyst I (164 g) was mixed with 164 g of 37 weight % HCl and 164 g ofwater to make a suspension. The suspension was heated to and at 90° C.for 2 hours to produce a heated suspension. Following the removal ofaqueous phase by decantation from the suspension, the solid was washedwith a running tap water for about 30 minutes and then dried at 125° C.for 2 hours. The dried solid was then calcined in air in a mufflefurnace at 500° C. for 4 hours to produce 158.58 g of an acid-leachedclay-bound ZSM-5 (catalyst J).

A portion (50 g) of catalyst J was steamed (20 ml H₂ O/hr) at 650° C. ina U-shape tube for 8 hours to produce an acid-leached (AL)-steamedzeolite (catalyst K).

In a separate run, 200 g of catalyst I was steamed as describedimmediately above to produce a steamed zeolite. The steamed zeolite (44g) was added to a flask containing 44 ml of H₂ O and 52 ml of HCl toproduce a suspension. The suspension was heated to and then at 90° C.for 2 hours. Following removal of the aqueous phase by decantation, thesolid was washed with running tap water for about 30 minutes. The washedsolid was dried in an oven at 125° C. for 3 hours followed bycalcination in a muffle furnace at 500° C. for 3 hours to produce 40.54g of steam and acid-leached zeolite (catalyst L).

The above catalysts I, J, K, and L were employed in a gasolinearomatization process for converting gasoline to olefins and BTX usingthe procedure disclosed in Example II. The purity of BTX was determinedby dividing the area % of BTX in a GC chromatogram by the area % of allproducts in the same GC chromatogram. The results are shown in Table IIIbelow.

                  TABLE III    ______________________________________               Product            Ratio               (weight %)         Olefins/                                          %    Catalyst     C.sub.2.sup.=                        C.sub.3.sup.=                               BTX  Purity                                          BTX   Coke    ______________________________________    I (PZ 2/50H + clay)                 7.3    9.2    36   97    .46   5.6    J (AL-catalyst I)                 8.1    7.3    40   97    .39   1.1    K (AL-steam-catalyst I)                 10.0   14.3   26   87    93    0.4    L (steam-AL-catalyst I)                 10.6   13.3   94   .80   0.4    ______________________________________     AL, acidleached; ALsteam; acidleaching followed by steam tratement;     steamAL; steam treatment followed by acidleaching.

Table III shows that commercially available PZ 2/50H zeolite probablyalso contained (contaminated with) some alumina binder which could beremoved by acid-leaching. The results in Table III also show thatacid-leaching substantially decreased coke formation (catalyst J). TableIII also shows that the coke content was further reduced and the ratioof olefins to BTX was further enhanced by an acid, steam, or both,treatment. Finally, Table III shows that the treatments of zeolitecatalyst described in the invention did not adversely affect the BTXpurity.

The results shown in the above examples clearly demonstrate that thepresent invention is well adapted to carry out the objects and attainthe ends and advantages mentioned as well as those inherent therein.While modifications may be made by those skilled in the art, suchmodifications are encompassed within the spirit of the present inventionas defined by the disclosure and the claims.

That which is claimed is:
 1. A composition comprising ZSM-5 zeolite,bentonite, and a coke suppressor which comprises tin oxide anddiatomaceous earth.
 2. A composition according to claim 1 wherein theweight ratio of bentonite to ZSM-5 zeolite is in the range of from about1:20 to about 20:1.
 3. A composition according to claim 1 wherein theweight ratio of bentonite to ZSM-5 zeolite is in the range of from about1:5 to about 5:1.
 4. A composition according to claim 1 wherein theweight ratio of coke suppressor to ZSM-5 zeolite is in the range of fromabout 1:20 to about 20:1.
 5. A composition according to claim 1 whereinthe weight ratio of coke suppressor to ZSM-5 zeolite is in the range offrom about 1:5 to about 5:1.
 6. A composition according to claim 1wherein the weight ratio of bentonite to ZSM-5 zeolite is in the rangeof from about 1:20 to about 20:1 and the weight ratio of coke suppressorto ZSM-5 zeolite is in the range of from about 1:20 to about 20:1.
 7. Acomposition according to claim 1 wherein the weight ratio of bentoniteto ZSM-5 zeolite is in the range of from about 1:5 to about 5:1 and theweight ratio of coke suppressor to ZSM-5 zeolite is in the range of fromabout 1:5 to about 5:1.
 8. A composition according to claim 1 whereinsaid tin oxide is stannous oxide.
 9. A composition according to claim 1further comprising a promoter selected from the group consisting ofsulfur, phosphorus, silicon, boron, zinc, titanium, zirconium,molybdenum, lanthanum, cesium, an oxide thereof, and combinations of twoor more thereof.
 10. A composition according to claim 9 wherein said tinoxide is stannous oxide.
 11. A composition comprising ZSM-5 zeolite,bentonite, and a coke suppressor which comprises tin oxide anddiatomaceous earth wherein the weight ratio of bentonite to ZSM-5zeolite is in the range of from about 1:20 to about 20:1 and wherein theweight ratio of coke suppressor to ZSM-5 zeolite is in the range of fromabout 1:20 to about 20:1.
 12. A composition according to claim 11wherein the weight ratio of bentonite to ZSM-5 zeolite is in the rangeof from about 1:5 to about 5:1 and the weight ratio of coke suppressorto ZSM-5 zeolite is in the range of from about 1:5 to about 5:1.
 13. Acomposition according to claim 11 wherein said tin oxide is a stannousoxide.
 14. A composition according to claim 11 further comprising apromoter selected from the group consisting of sulfur, phosphorus,silicon, boron, zinc, titanium, zirconium, molybdenum, lanthanum,cesium, an oxide thereof, and combinations of two or more thereof.
 15. Acomposition according to claim 14 wherein said tin oxide is stannousoxide.
 16. A composition comprising ZSM-5 zeolite, bentonite, and a cokesuppressor which comprises stannous oxide and diatomaceous earth whereinthe weight ratio of bentonite to ZSM-5 zeolite is in the range of fromabout 1:5 to about 5:1 and the weight ratio of coke suppressor to ZSM-5zeolite is in the range of from about 1:5 to about 5:1.
 17. Acomposition according to claim 16 further comprising a promoter selectedfrom the group consisting of sulfur, phosphorus, silicon, boron, zinc,titanium,. zirconium, molybdenum, lanthanum, cesium, an oxide thereof,and combinations of two or more thereof.
 18. A composition comprisingZSM-5 zeolite, bentonite a coke suppressor which comprises tin oxide anddiatomaceous earth, and a promoter selected from the group consisting ofsulfur, phosphorus, silicon, boron, zinc, titanium, zirconium,molybdenum, lanthanum, cesium, an oxide thereof, and combinations of twoor more thereof.
 19. A composition according to claim 18 wherein saidtin oxide is stannous oxide.
 20. A composition comprising ZSM-5 zeolite,bentonite a coke suppressor which comprises tin oxide and diatomaceousearth, and a promoter selected from the group consisting of sulfur,phosphorus, silicon, boron, zinc, titanium, zirconium, molybdenum,lanthanum, cesium, an oxide thereof, and combinations of two or morethereof wherein the weight ratio of bentonite to ZSM-5 zeolite is in therange of from about 1:20 to about 20:1 and the weight ratio of cokesuppressor to ZSM-5 zeolite is in the range of from about 1:20 to about20:1.
 21. A composition according to claim 20 wherein said tin oxide isstannous oxide.
 22. A composition comprising ZSM-5 zeolite, bentonite,and a coke suppressor which comprises stannous oxide and diatomaceousearth, and a promoter selected from the group consisting of sulfur,phosphorus, silicon, boron, zinc, titanium, zirconium, molybdenum,lanthanum, cesium, an oxide thereof, and combinations of two or morethereof wherein the weight ratio of bentonite to ZSM-5 zeolite is in therange of from about 1:5 to about 5:1 and the weight ratio of cokesuppressor to ZSM-5 zeolite is in the range of from about 1:5 to about5:1.